1. Field of the Invention
This invention relates to a video data recording apparatus, particularly a video data recording apparatus for recording video data and search data.
2. Description of the Related Art
VTRs (Video Tape Recorders) have been publicly known as apparatuses for recording video data. In recent years, digital VTRs have been also publicly known which employ a digital recording method. These digital VTRs convert video information into digital signals, and record them on magnetic tapes after having processed them by high-efficiency compression encoding, error-correction encoding and the required modulation. To reproduce records on magnetic tapes, they demodulate the signals reproduced by their corresponding reproducing heads, correct any errors caused by the magnetic tapes (for example, due to dust or flaws on the tapes) by using error-correction codes, and decode the corrected signals to restore the recorded video information.
These conventional digital video data recording apparatuses are designed so as to record a picture of video data on plural tracks in the recording track pattern as shown in FIG. 1; example, video signals in the first field are recorded on tracks T1, T2 and T3, and those in the second field are recorded on tracks T4, T5 and T6. Signals are thus distributed on plural tracks corresponding to a picture of video data for the purposes of processing many data of digital video signals and implementing a search facility and special reproducing facilities such as slow reproduction and search reproduction easily.
In recent years, the high-efficiency video data encoding technology has been rapidly advanced mainly in the telecommunication fields such as television conference system and television telephone system and digital VTRs have encountered an increasing demand for the long-time recording capability. Therefore, it is expected that the high-efficiency video data encoding technology will be applied to digital VTRs to increase the recording time in the digital VTRs. Even if the recording time is slightly increased, no ratio of whole numbers may be obtained in a vertical synchronizing period between rotary head rotation and video signal, or the vertical synchronizing signals for rotary head rotation and video signal may be asynchronized by variable-length encoding and time-base correlation processing. In this case, the following problem is encountered: Considering a high-speed search function to identify the address of each picture element in video signals in reference to a vertical synchronizing signal, it is necessary for the vertical synchronizing signal to be located at a constant position on every track in the recording track pattern of a recording medium. However, the recording positions of vertical synchronizing signals are different between tracks, if the recording time is longer. In short, it is more difficult to implement the special reproducing and picture search facilities, if the recording time is longer.